The present invention relates to a method and apparatus for monitoring and measuring audience exposure to radio programming, television programming, audio and video recordings and the like. Since its origins in the mid-1960's the basic data collection instrument for radio audience estimates of The Arbitron Company of Columbia, Md. (“Arbitron”) has been a one week diary which Arbitron “respondents” were asked to fill out. The diaries were then mailed to Arbitron's central processing facility in Columbia, Md., photographed and keypunched. The radio audience measurement data was then calculated from the information contained in the diaries.
Human nature being what it is, the diary methodology was less a moment-by-moment account of radio exposure and more a means of recording recollected exposure. Studies have shown that most diaries were routinely filled out only daily or at the end of the diary week rather than at the time of radio listening. While this may be a significant disadvantage, compared to other available methodologies, such as telephone canvassing and recall, the diary proved to deliver reasonably stable and believable audience estimates.
As a consequence, Arbitron became, and remains, a dominant radio audience measurement firm in the United States and is the only supplier of radio audience estimates in the larger radio markets. Every year billions of advertising dollars flow into U.S. radio stations and networks based on Arbitron audience estimates.
Various attempts have been made to simplify the process and system of monitoring audience exposure to radio and television programming. In one such system, disclosed in the U.S. Pat. No. 5,382,970, a “portable data meter” is provided for each radio listener or television viewer which records the identity of a radio station or TV channel that is being currently listened to or watched. This station or channel data is stored in association with the current date and time and later transmitted to a central computer via a built-in cellular telephone. The subject matter of this patent is incorporated herein by reference.
One drawback of this patented system is inherent in the information that is stored and forwarded. For TV monitoring the system receives the channel selection by intercepting the infra-red transmissions of a TV remote control. For radio monitoring the user must press a station selection button on the data meter in addition to changing the station on the radio dial. This is not only inconvenient, but this system can result in inaccuracies if the person carrying the data meter does not point the TV remote at it whenever a TV channel is selected, or does not press the station selection button when selecting a radio station.
To ensure that each person monitored is actually in the same room as, and actually hears, the television or radio programming which is allegedly being watched or listened to, the portable data meter is provided with means to issue a “warning” when certain inaudible sounds produced by a television or radio loudspeaker are not received by a built-in microphone. To facilitate this operation, the broadcast signal from the various broadcast stations that may be selected have an additional signal imposed on their sound carrier outside the normal audio range. Each portable data meter is provided with a sound detector for this additional signal and a warning device such as a beeper. The processor within the data meter is made responsive to the receipt of the additional signal to activate the warning device and then to commence the recording of data only if and when the owner of the data meter presses a button or the like to signal his/her presence.
In the early 1990's Arbitron began to develop what has become known as the “Portable People Meter”, also known as “Personal People Meter” or “PPM”. The structure and operation of the PPM are disclosed in the U.S. Pat. Nos. 5,579,124 and 5,450,490, both assigned to Arbitron. The subject matter of these two patents is also incorporated herein by reference.                The Arbitron PPM system operates generally as follows:        1. Broadcasters, cable operators and record companies encode their audio streams using an Arbitron supplied unit which inserts inaudible code information. The codes may identify each program segment (e.g. song, commercial, radio show or the like) as it is transmitted or played. Alternatively or in addition, the codes may identify the TV channel or radio station that is broadcasting, without further identifying the particular program material or segment that is being broadcast. Any and all program identifying information, which is identified by the codes received and decoded, such as by a Personal People Meter, are denoted hereinafter as “program-identifying” (“PI”) information. The inaudible (or audible) code information which identifies program material segments (songs, commercials, radio shows) is denoted hereinafter as “program material-identifying” (“PMI”) information.        2. Respondents (persons used in the audience measurement) carry the pager-sized Personal People Meter which contains a motion sensor, a clock and a means, including a microphone, for receiving, detecting and recording the codes when the wearer is exposed to an encoded audio stream. The clock is used to determine and record the date, time and duration of exposure.        3. At the end of each day respondents place the PPM into a cradle which is plugged into the respondent's home electrical system. The cradle recharges the meter's battery and extracts the recorded exposure data, sending it to a household hub which is attached to both the home electrical supply and the home telephone wire line.        4. At some time during the night, the household hub is interrogated via telephone by a central computer and the stored data is downloaded.        
While the Personal People Meter is an extremely useful and convenient device for gathering data regarding audience exposure to electronic media, it has a number of drawbacks.                1. There is no inherent benefit to a respondent to reliably carry the PPM. Although Arbitron rewards respondents with small cash awards and points for compliance toward larger prizes, these benefits are indirect and are not a strong incentive to maintain full compliance.        2. The PPM system is an inherently “home based” concept. Although the Meter itself may be carried anywhere, it must be returned to its charging cradle at the end of each day to recharge its batteries and unload its data to the household hub for transmission to Arbitron. This data collection method fails if the respondent does not return home every night.        